Fixed ZipEntryFileObject.GetStream()

GetStream was returning bad results. Turned out the window was trying to
get the bitmap twice which was opening the stream twice. The zip file
doesn't like having more than one stream accessing it at the same time.
Will have to do some more to make sure it doesn't happen other places.
removed zip dll ref from the ImageViewer prof
Added some style to the listview

not even good style. more of a placeholder at the moment
repository was treating a zip file as just another file

repository was treating a zip file as just another file rather than as a
directory
made populating listview async

now the directory list will blank out when it changes dir before it
repopulates itself. It means that if it takes a while to get the new
dir's contents it doesn't look like the app has hung